The present invention relates to a method for the manufacture of a single-rotation machine having an internal axis, whose external rotor has at least three axially parallel, one-part engagement parts, which are interconnected by terminal side parts, the external and internal rotors being sealed with respect to one another and with respect to a casing forming a sealing gap.
The invention also relates to a single rotation machine manufactured according to the inventive method and to an assembly body for use in the inventive method.
Single-rotation machines having an internal axis, in which sealing does not take place by sealing ledges, have the advantage of low friction losses at the sealing points, because sealing takes place in a contact-free manner by the forming of a sealing gap by the parts moving relative to each other. Thus, such single-rotation machines are suitable for high rotational speeds so that, in the case of compact construction, they can be used as a supercharger on an internal combustion engine.
However, the accuracy of manufacture of known manufacturing methods is not adequate to obtain good sealing through narrow sealing gaps. Variations from the kinematically ideal shape are obtained on producing the curvature of the engagement surfaces of the two rotors and during the reciprocal association of the engagement parts of the external rotor in the tangential and radial direction, as well as during the assembly of the rotors relative to one another and relative to the surrounding casing. As the different divergences can be summated at specific sealing areas, it is necessary to provide wide sealing gaps, which take account of the summated maximum manufacturing and assembly tolerances, so as to prevent contact at the sealing points. The resulting wide sealing gaps of single-rotation machines manufactured in the conventional manner lead to poor machine efficiency as a result of sealing losses. The single-rotation machines of the above-mentioned type known from the literature have not gone into mass production as a result of the complicated, costly and imprecise manufacturing methods, or they are only provided for the passage of liquid media and operated at the relatively low rotational speeds suitable in such cases.
U.S. Pat. No. 1,753,476 shows a construction of a known single-rotation machine in which, for simplifying manufacture, it has been necessary to accept geometrically simple, but kinematically imprecise engagement faces with the resulting wide sealing gaps, so that it is only suitable for feeding relatively viscous media. Its external rotor is manufactured in one piece, its engagement parts are held at one side of a rotor side portion and can consequently only be loaded by limited centrifugal forces or can only have a short axial extension.